I just realized that one of the bolts are missing to my 4-2-1 2-piece DC Sport SS Header and its been making some really weird rattling noise when i hit 2500rpm's. I dunno if this will fix the problem but I would like that bolt back up on there.
thanks

 

I don't know the size off hand but DC Sports phone # is 909-734-2030.

You may be describing the same noise I've got. Same 2500 but all my bolts are in and tight. Turns out to be something loosened up in the flex joint. The only way I was able to identify it was to wrap the joint tightly in header wrap. Noise didn't go completely away but it is greatly reduced. DC is supposedly sending me a new A pipe but its been since Oct.

 

same thing happen to me about a month ago, i am using a stock bolt from the old header seems to hold up for about a month now, i pulled off my header and took it to everwhere to find a match but couldn't get one. sorry i forgot the bolt spec.